Alpha Reduced Shank HSS Jobber Drill Bit have a smaller diameter at their shank than at their tip. This allows them to drill large holes while being compatible with tools that have a small chuck size Features / Benefits: The end of the drill bit has a 12.7mm non-slip shank that has 3 flat sides which when installed into a 10mm or 12mm chuck prevents slippage. All material is advisory only and its use by anyone is entirely voluntary. Reliance on it for any purpose by anyone is at the sole risk of that person and Bolt and Nut Australia is not responsible for any loss claim or damages arising therefrom.